Pharmacodynamic differences between canagliflozin and dapagliflozin: results of a randomized, double-blind, crossover study

AIMS

To compare the pharmacodynamic effects of the highest approved doses of the sodium glucose co-transporter 2 (SGLT2) inhibitors canagliflozin and dapagliflozin on urinary glucose excretion (UGE), renal threshold for glucose excretion (RTG ) and postprandial plasma glucose (PPG) excursion in healthy participants in a randomized, double-blind, two-period crossover study.

METHODS

In each treatment period, participants (n = 54) received canagliflozin 300 mg or dapagliflozin 10 mg for 4 days (20 min before breakfast). A mixed-meal tolerance test (600 kcal; 75 g glucose) was performed at baseline and on day 4 of each treatment period to assess changes in incremental PPG (PPGΔAUC0-2 h ). We measured 24-h UGE and plasma glucose on day 4 to determine 24-h mean RTG .

RESULTS

Canagliflozin 300 mg and dapagliflozin 10 mg had similar effects on UGE and RTG for 4 h after dosing, but canagliflozin was associated with higher UGE and greater RTG reductions for the remainder of the day. Mean 24-h UGE was ∼25% higher with canagliflozin than with dapagliflozin (51.4 vs. 40.8 g), and 24-h mean RTG was ∼0.4 mmol/l (7 mg/dl) lower with canagliflozin than with dapagliflozin (3.79 vs. 4.17 mmol/l; p < 0.0001). Dapagliflozin had no effect on PPG excursion; canagliflozin delayed and reduced PPG excursion (between-treatment difference in PPGΔAUC0-2 h from baseline expressed as a percentage of baseline mean, -10.2%; p = 0.0122). Canagliflozin and dapagliflozin were generally well tolerated.

CONCLUSIONS

In healthy participants, canagliflozin 300 mg provided greater 24-h UGE, a lower RTG and smaller PPG excursions than dapagliflozin 10 mg.

Effect of the sodium glucose co-transporter 2 inhibitor canagliflozin on plasma volume in patients with type 2 diabetes mellitus

AIM

To evaluate the effects of canagliflozin on plasma volume, urinary glucose excretion (UGE), fasting plasma glucose (FPG), glycated haemoglobin (HbA1c) and additional measures of fluid/electrolyte balance in patients with type 2 diabetes on background therapy with metformin and angiotensin-converting enzyme inhibitors or angiotensin receptor blockers.

METHODS

Patients (N = 36) were randomized (1:1) to receive canagliflozin 300 mg or placebo for 12 weeks. Pharmacodynamic parameters were assessed at baseline and at weeks 1 and 12.

RESULTS

Increased 24-h UGE was seen in the canagliflozin group compared with a reduction in the placebo group at both week 1 (91.8 vs. -2.4 g) and week 12 (82.6 vs. -0.4 g). Canagliflozin also reduced both FPG and HbA1c. Reductions in body weight and blood pressure were observed at weeks 1 and 12. Canagliflozin decreased plasma volume compared with an increase with placebo at week 1 (-5.4 vs. 4.3%; p = 0.02), but this was largely attenuated at week 12 (4.6 vs. 5.8%; p = 0.76). A modest numerical increase in urine volume was observed with canagliflozin at week 1 that was attenuated at week 12; other measures of volume status (i.e. blood urea nitrogen, serum creatinine and haematocrit) remained modestly increased with canagliflozin at week 12.

CONCLUSION

Canagliflozin provided sustained effects on UGE and FPG over 12 weeks and a transient reduction in plasma volume that was largely attenuated by week 12.

CCR2 antagonism in patients with type 2 diabetes mellitus: a randomized, placebo-controlled study

AIMS

Macrophage recruitment through C-C motif chemokine receptor-2 (CCR2) into adipose tissue is believed to play a role in the development of insulin resistance and type 2 diabetes mellitus (T2DM). The objective of this Phase 2 proof-of-concept study was to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of JNJ-41443532, an orally bioavailable CCR2 antagonist, in patients with T2DM.

METHODS

This was a 4-week, double-blind, placebo-controlled, randomized, multicenter study. A total of 89 patients were randomized to receive either 250- or 1000-mg of JNJ-41443532 twice daily, 30-mg of pioglitazone once daily (reference arm), or placebo. The primary endpoint was change from baseline in 23-h weighted mean glucose (WMG); secondary endpoints included change from baseline in fasting plasma glucose (FPG), insulin resistance (Homeostatic Model Assessment [HOMA-IR]), insulin secretion (HOMA-%B) and body weight.

RESULTS

Absorption of JNJ-41443532 into the systemic circulation occurred at a median tmax of 2 h, and the mean t½ was approximately 8 h for both doses; plasma systemic exposures increased slightly more than dose-proportionally. After 4 weeks, reductions in 23-h WMG and FPG were observed in all treatment groups compared with placebo and were significantly lower for 250-mg JNJ-41443532 and pioglitazone. HOMA-IR was lower for all treatment groups, but significantly lower only for pioglitazone. Conversely, HOMA-%B was increased for all groups, but significantly increased only for 250-mg JNJ-41443532. All groups, including placebo, had decreased body weight over time. There were no clinically significant findings during routine safety assessments and the incidence of treatment-emergent adverse events was similar across all groups.

CONCLUSIONS

Administration of JNJ-41443532 resulted in modest improvement in glycaemic parameters compared with placebo, and was generally well tolerated in patients with T2DM.

Canagliflozin, a novel inhibitor of sodium glucose co-transporter 2, dose dependently reduces calculated renal threshold for glucose excretion and increases urinary glucose excretion in healthy subjects

Canagliflozin, a potent, selective sodium glucose co-transporter 2 inhibitor in development for treatment of type 2 diabetes, lowers plasma glucose (PG) by lowering the renal threshold for glucose (RT(G) ) and increasing urinary glucose excretion (UGE). An ascending single oral-dose phase 1 study investigated safety, tolerability and pharmacodynamics of canagliflozin in healthy men (N = 63) randomized to receive canagliflozin (n = 48) or placebo (n = 15). Canagliflozin (10, 30, 100, 200, 400, 600 or 800 mg q.d. or 400 mg b.i.d.) was administered to eight cohorts (six subjects/cohort: canagliflozin; two subjects/cohort: placebo). Dose dependently, canagliflozin decreased calculated 24-h mean RT(G) with maximal reduction to approximately 60 mg/dl, and increased mean 24-h UGE. At doses >200 mg administered before breakfast, canagliflozin reduced postprandial PG and serum insulin excursions at that meal. Canagliflozin was generally well tolerated; most adverse events were mild and no hypoglycaemia was reported. These results support further study of canagliflozin.

Effect of aprepitant on the pharmacokinetics and pharmacodynamics of warfarin

OBJECTIVE

To examine the effect of aprepitant on the pharmacokinetics and pharmacodynamics of warfarin. Aprepitant is a neurokinin-1 (NK1)-receptor antagonist developed as an antiemetic for chemotherapy-induced nausea and vomiting.

METHODS

This was a double-blind, placebo-controlled, randomized, two-period, parallel-group study. During period 1, warfarin was individually titrated to a stable prothrombin time (expressed as international normalized ratio, INR) from 1.3 to 1.8. Subsequently, the daily warfarin dose remained fixed for 10-12 days. During period 2, the warfarin dose was continued for 8 days, and on days 1-3 administered concomitantly with aprepitant (125 mg on day 1, and 80 mg on days 2 and 3) or placebo. At baseline (day -1 of period 2) and on day 3, warfarin pharmacokinetics was investigated. INR was monitored daily. During period 2, warfarin trough concentrations were determined daily.

RESULTS

The study was completed by 22 healthy volunteers (20 men, 2 women). On day 3, steady-state pharmacokinetics of warfarin enantiomers after aprepitant did not change, as assessed by warfarin AUC(0-24 h) and C(max). However, compared with placebo, trough S(-) warfarin concentrations decreased on days 5-8 (maximum decrease 34% on day 8, P<0.01). The INR decreased after aprepitant with a mean maximum decrease on day 8 of 11% versus placebo (P=0.011).

CONCLUSION

These data are consistent with a significant induction of CYP2C9 metabolism of S(-) warfarin by aprepitant. Subsequently, in patients on chronic warfarin therapy, the clotting status should be monitored closely during the 2-week period, particularly at 7-10 days, following initiation of the 3-day regimen of aprepitant with each chemotherapy cycle.

Safety, tolerability, and pharmacokinetics of an extended-release formulation of fluvastatin administered once daily to patients with primary hypercholesterolemia

Fluvastatin sodium (Lescol, Novartis Pharmaceutical Corp., East Hanover, NJ, U.S.A.), a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG Co-A) reductase inhibitor that limits cholesterol biosynthesis, is available as a 40-mg immediate-release formulation capsule. An extended-release formulation for once-daily administration has been developed for patients with primary hypercholesterolemia who may benefit from doses higher than 40 mg/day. This phase I study evaluated the safety, tolerability, and pharmacokinetics of a new fluvastatin extended-release formulation at doses ranging from 80-640 mg/day in 40 hypercholesterolemic patients. After a 2-week dietary stabilization phase, patients (Fredrickson type IIa/IIb), 18-55 years of age, were randomly assigned to four groups to receive oral fluvastatin extended-release (80, 160, 320, or 640 mg) or matching placebo once daily for 13 days. Fluvastatin extended-release was generally safe and well tolerated at doses of 80-320 mg/day. Within this dose range, linear pharmacokinetics was observed after single and multiple dosing. At 640 mg, fluvastatin extended-release was not well tolerated. Six of the seven actively treated patients at this dose experienced adverse events, including diarrhea, headache, and clinically relevant elevations in serum transaminase concentrations. In addition, nonlinear pharmacokinetics, possibly due to saturation of first-pass metabolism, was observed at this dose, causing higher than expected serum drug concentrations. Once-daily administration of fluvastatin extended-release at doses of 80-320 mg/day was generally safe and well tolerated in patients with primary hypercholesterolemia over a 13-day dosing period.

Insulin and insulinomimetic agents induce activation of phosphatidylinositol 3'-kinase upon its association with pp185 (IRS-1) in intact rat livers

The major cytosolic substrate of the insulin receptor is a 185-kDa phosphoprotein (IRS-1) that contains multiple putative attachment sites for the p85 alpha regulatory subunit of phosphatidylinositol 3'-kinase (PI3K). To examine the possible interaction of pp185 with p85 alpha in vivo, we injected insulin or insulinomimetic agents (a combination of H2O2 and vanadate (H/V)) into the portal vein of anesthetized rats. IN this model system, H/V treatment and, to a lesser extent, injection of insulin resulted in rapid and sustained tyrosine phosphorylation of multiple cellular proteins, including pp185/IRS-1. The latter was found to undergo specific association with the p85 alpha regulatory subunit of PI3K but not with two other proteins that contain src homology domains. As p85 alpha was not detectably phosphorylated on tyrosine residues and did not appear to interact directly with the insulin receptor, we conclude that tyrosine phosphorylation of pp185 promotes its association with p85 alpha and the catalytic subunit of PI3K. The recruitment of the holoenzyme may also involve its enzymatic activation and thus constitute an important step in the transduction of insulin signals.

Structure of the insulin receptor substrate IRS-1 defines a unique signal transduction protein

Since the discovery of insulin nearly 70 years ago, there has been no problem more fundamental to diabetes research than understanding how insulin works at the cellular level. Insulin binds to the alpha subunit of the insulin receptor which activates the tyrosine kinase in the beta subunit, but the molecular events linking the receptor kinase to insulin-sensitive enzymes and transport processes are unknown. Our discovery that insulin stimulates tyrosine phosphorylation of a protein of relative molecular mass between 165,000 and 185,000, collectively called pp185, showed that the insulin receptor kinase has specific cellular substrates. The pp185 is a minor cytoplasmic phosphoprotein found in most cells and tissues; its phosphorylation is decreased in cells expressing mutant receptors defective in signalling. We have now cloned IRS-1, which encodes a component of the pp185 band. IRS-1 contains over ten potential tyrosine phosphorylation sites, six of which are in Tyr-Met-X-Met motifs. During insulin stimulation, the IRS-1 protein undergoes tyrosine phosphorylation and binds phosphatidylinositol 3-kinase, suggesting that IRS-1 acts as a multisite 'docking' protein to bind signal-transducing molecules containing Src-homology 2 and Src-homology-3 domains. Thus IRS-1 may link the insulin receptor kinase and enzymes regulating cellular growth and metabolism.

Evaluation of the sexual consequences of surgery: retrospective and prospective strategies

To assess the impact of a stressor, it is desirable to evaluate affected individuals' status both prior to and following a stressful event. Because of the difficulties inherent in prospective designs, investigators often ask people who have experienced an aversive event to evaluate their prestressor adjustment retrospectively. Do such retrospective evaluations provide a reasonable alternative to prospective assessment? To answer this question we compared retrospective and prospective data gathering procedures in the evaluation of sexual adjustment after prostate surgery. One hundred fifty-two married males who had undergone prostatectomy for benign prostatic enlargement completed a battery of measures which evaluated pre- and postsurgical sexual adjustment either prospectively (i.e., before and after surgery) or retrospectively (i.e., ratings made after surgery of both pre- and postsurgical adjustment). Retrospective assessment indicated considerable sexual deterioration pre- to postsurgery. In subjects tested prospectively, however, the results showed that surgery had little impact on sexual adjustment. Moreover, direct comparisons of retrospective and prospective methodologies reveal that discrepancies are due to differences in evaluations of presurgery status, with retrospective evaluation yielding more favorable ratings than prospective assessment. The results highlight a variety of biases which may affect self-ratings of pre- and post-stressor adaptation and show that discrepancies associated with the two methodologies have important implications for understanding the impact of a stressor on adjustment.

Vanadate normalizes hyperglycemia in two mouse models of non-insulin-dependent diabetes mellitus

We have studied the effects of oral administration of vanadate, an insulinometic agent and a potent inhibitor of phosphotyrosyl protein phosphatase (PTPase) in vitro, on blood glucose and PTPase action, in two hyperinsulinemic rodent models of non-insulin-dependent diabetes mellitus (NIDDM). Oral administration of vanadate (0.25 mg/ml in the drinking water) to ob/ob mice for 3 wk lowered blood glucose level from 236 +/- 4 to 143 +/- 2 mg/dl without effect on body weight. Administration of vanadate to db/db mice produced a similar effect. Electron microscopic examination revealed no signs of hepatotoxicity after 47 d of treatment. There was a slight reduction in insulin receptor autophosphorylation when tested by immunoblotting with antiphosphotyrosine antibody after in vivo stimulation, and the phosphorylation of the endogenous substrate of the insulin receptor, pp185, was markedly decreased in the ob/ob mice. Both cytosolic and particulate PTPase activities in liver of ob/ob mice measured by dephosphorylation of a 32P-labeled peptide corresponding to the major site of insulin receptor autophosphorylation were decreased by approximately 50% (P less than 0.01). In db/db diabetic mice, PTPase activity in the cytosolic fraction was decreased to 53% of control values (P less than 0.02) with no significant difference in the particulate PTPase activity. Treatment with vanadate did not alter hepatic PTPase activity as assayed in vitro, or receptor and substrate phosphorylation as assayed in vivo, in ob/ob mice despite its substantial effect on blood glucose. These data indicate that vanadate is an effective oral hypoglycemic treatment in NIDDM states and suggest that its major effects occurs distal to the insulin receptor tyrosine kinase.

Activation of Na+/H+ exchange by epidermal growth factor elevates intracellular pH in A431 cells

Epidermal growth factor (EGF) increases Na+ uptake in several cell types through an electroneutral, amiloride-sensitive pathway putatively identified as Na+/H+ countertransport. We have previously shown (Rothenberg, P., Glaser, L., Schlesinger, P., and Cassel, D. (1983) J. Biol. Chem. 257, 4883-4889) that EGF rapidly activates amiloride-sensitive net Na+ influx in the A431 human epidermoid carcinoma cell line. We also described the presence of transmembrane, amiloride-sensitive Na+/H+ exchange in A431 cells using a new fluorescence technique for the measurement of intracellular pH (pHi) based on the incorporation of fluorescein-dextran into the cell cytoplasm. The low pKa of fluorescein (approximately 6.4) prevented the direct assessment of the inferred, EGF-induced cytoplasmic alkalinization, mediated by stimulated Na+/H+ exchange. In this paper, 4',5'-dimethylfluorescein (pKa 6.75) was coupled to dextran, allowing increased pH sensitivity of the fluorescence assay in the physiological range. Using this improved assay, basic features of pHi regulation in A431 cells are documented, including the role of Na+/H+ exchange and Na+-linked C1-/HCO3-exchange in acid extrusion. We directly demonstrate a rapid elevation of pHi by addition of EGF as well as by serum in A431 cells. The pHi increase is half-maximal at 5-10 ng/ml of EGF, is dependent on external Na+, independent of external Ca2+, and inhibited by millimolar amiloride. EGF and serum also enhance Na+/H+ exchange-mediated cytosolic acidification when the transmembrane Na+ concentration gradient favors Na+ efflux from the cells. An alkaline pHi shift, caused by activation of Na+/H+ exchange, may be an important primary event in the mechanism of EGF action.

Platelet-derived growth factor stimulates Na+/H+ exchange and induces cytoplasmic alkalinization in NR6 cells

Stimulation of Na+/H+ exchange by growth factors has been implicated as a mechanism allowing quiescent cells to resume growth because of a predicted elevation of intracellular pH(pHi). We tested this prediction in NR6 cells by using a further development of our technique for pHi measurement, based on introduction of the fluorescent pH indicator 4',5'-dimethylfluorescein (pKa = 6.75) coupled to dextran into the cytoplasm. Addition of the potent mitogens platelet-derived growth factor (PDGF) or serum to NR6 cells stimulates an amiloride-sensitive 22Na+ uptake and causes an elevation of pHi. The PDGF-dependent pHi increase follows a lag period of approximately equal to 2 min, reaches a maximal level within 10 min (delta pHi approximately equal to 0.1 at an external pH of 7.18), and remains at this level for at least 1 hr. Serum addition initially produces a large elevation of pHi, which later declines to a level similar to that obtained with PDGF. The effects of PDGF and serum are partially additive (delta pHi approximately equal to 0.14). The magnitude of pHi elevation by PDGF decreases with increasing extracellular pH. Serum- and PDGF-dependent elevations of pHi are inhibited by amiloride and by eliminating Na+ from the medium. Under conditions in which Na+/H+ exchange is inhibited, PDGF and serum induce an initial cytoplasmic acidification that does not show a lag period. The results show that a single purified growth factor, as well as serum, can promote a sustained elevation of pHi by stimulating Na+/H+ exchange. The extent of pHi elevation may be modulated by the concomitant stimulation by the growth factor of a process generating H+ within the cell.

Epidermal growth factor stimulates amiloride-sensitive 22Na+ uptake in A431 cells. Evidence for Na+/H+ exchange

Epidermal growth factor (EGF) increases Na+ uptake in several cell types through an electroneutral, amiloride-sensitive pathway putatively identified as Na+/H+ countertransport. The inferred cytosolic alkalinization resulting from this process has been proposed to be an important component of mitogenic stimulation. We studied the effect of EGF on the Na+/H+ exchange system of A431 cells, a cell line having a very high EGF receptor density but which is not mitogenically stimulated by EGF. We demonstrate that EGF rapidly activates net Na+ influx in A431 cells. Amiloride inhibits the EGF-dependent Na+ uptake (65% inhibition at 3 mM, ID50 approximately 0.3 mM) and inhibits much less the EGF-independent uptake. EGF is known to enhance 45Ca+ accumulation in A431 cells (Sawyer, S. T., and Cohen, S. (1981) Biochemistry 20, 6280-6286). The following findings indicate that EGF-dependent 22Na+ and 45Ca2+ uptake are two independent processes. 1) EGF effectively stimulates an amiloride-sensitive 22Na+ uptake in the absence of external Ca2+. 2) EGF-dependent 45Ca2+ uptake is not inhibited by amiloride. A new fluorescence technique is described for intracellular pH determination based on the introduction of fluorescein-labeled dextran into the cell cytoplasm. Using this method, the presence of amiloride-sensitive Na+/H+ exchange in A431 cells is documented. Although the lack of pH sensitivity of fluorescein fluorescence above pH 7.3-7.4 prevents a direct assessment of an EGF-induced increase of intracellular pH, the combined results of 22Na+ flux and intracellular pH measurements suggest that EGF activates Na+/H+ exchange in A431 cells. We conclude that enhanced Na+/H+ exchange may not necessarily be coupled to mitogenic triggering in different cell types, although the stimulation of Na+/H+ exchange may constitute a primary event in the mechanism of EGF action.

Serum and epidermal growth factor transiently depolarize quiescent BSC-1 epithelial cells

Continuous intracellular recording of membrane potential with microelectrodes in BSC-1 epithelial cells has been used to study the early ionic effects of the interaction of mitogens with cell surface receptors. Initial results show that (i) there is no significant difference in membrane potential between growing and quiescent cells, (ii) addition of epidermal growth factor or serum to quiescent BSC-1 cells induces a brief and transient depolarization, (iii) the mitogenic response of BSC-1 cells to epidermal growth factor and the transient depolarization show similar concentration dependences, and (iv) serum addition to quiescent BSC-1 cells induces a sustained increase in Na+ influx that is electroneutral and amiloride sensitive. Intracellular pH changes may be a primary event triggering the response of quiescent cells to mitogenic polypeptides.